说明：  1.加深理解数字滤波器与连续时间滤波器之间的技术指标转化。 2.掌握脉冲响应不变法设计IIR数字滤波器的优缺点及使用范围
(1.Deepen the understanding of the technical index transformation between digital filter and continuous time filter. 2. Master the advantages, disadvantages and application scope of the design of IIR digital filter by the pulse response invariant method)